Composition and method of inhibiting corrosion of ferrous metals by amine-stabilized unsaturated chlorinated hydrocarbons



Unite Detroit, Mich., a corporation of Michigan No Drawing. Filed June 10, 1958, Ser. No. 741,001 14 Claims. (Cl. 252-471) copending application Serial No. 445,474, filed July 23, 1954, and now abandoned.

This invention relates to a composition and method of inhibiting the corrosion of ferrous metals by aminestabilized, unsaturated chlorinated hydrocarbons, particularly those chlorinated hydrocarbons which decompose under the influence of metals or oxygen to form acidic products. Among the chlorinatedhydrocarbons inhibited in accordance with this invention are the unsaturated chlorinated hydrocarbons such as 1,2 dichloroethylene, trichlorethylene, perchlorethylene, the chloropropylenes, the chlorobutylenes and the chlorobutadienes. All such unsaturated chlorinated hydrocarbons have low molecular weights and are subject to decomposition'by metals or oxygen, or in their presence, and this decomposition is accelerated by light and heat.

It is conventional in the art to add stabilizers of various types to chlorinated hydrocarbons. Among the accepted stabilizers are the phenolic compounds, aryl amines, and various azo compounds. However, the use of such compounds is quite limited except in the case of a few of the higher boiling chlorinated hydrocarbons, since the stabilizers also have relatively high boiling points. A wide difference in boiling points between the solvent and the stabilizer is undesirable because of the difficulty of stabilizing the vapor phase, and it is desirable to provide a combination of solvent and stabilizer not having a wide difference in boiling points.

The organic amine bases have enjoyed widespread use as stabilizers for unsaturated chlorinated hydrocarbons. Such bases, including. primary aliphatic amines having the NH radical and basic cyclic compounds characterized by nitrogen in the ring such as pyridine and the like are disclosed in the patents to Dinley, Numbers 2,096,735, 2,096,736 and 2,096,737. "Under many conditions the primary aliphatic and cyclic amine bases disclosed in the Dinley patents are highly effective and desirable stabilizers --for chlorinated hydrocarbons.

In the manufacture of the unsaturated chlorinated hydrocarbons as trichlorethylene, for example,-the recovery of a neutral, sweet, relatively pure product is almost impossible without the use of a stabilizer such as these amines. The amine stabilizer should be present in the efining operation, as distinguished from adding amine to there-fined product, and the amine should be volatile with l the chlorinated hydrocarbon and therefore carry over from the refining operation into the refined product. Unless a neutral, sweet product is obtained when the solvent is refined, subsequent attempts to stabilize the solvent often prove futile, or at least extremely costly and time consuming. Thus, the amines are not only highly effective and desirable stabilizers, but their use in both the liquid and vapor in the last stages of manufacture is almost essential.

Yet, in spite of the effectiveness and desirability of the amines as stabilizers, there appears to have been an undesirable reaction or set of reactions which take place when the amines are used as stabilizers in unsaturated chlorinated hydrocarbon solvents in the presence of certain metals of the iron group. It has now been discovered that the lower boiling unsaturated chlorinated hydrocar- This application is a continuation-in-part of applicants States Patent 16 Mich, assignors to Detrex Chemical Industries, Inc.,

3,031,410 Patented Apr. 24, 1962 bons, when stabilized with certain of the conventional organic amines, such amines having boiling points which are not widely different from the boiling point of the chlorinated hydrocarbon, appear to enter into a complex reaction when exposed to one of those metals. The reaction appears to be metal-induced, causing a progressive decomposition of the chlorinated hydrocarbons. The reaction which occurs in the presence of conventional amines causes attack on the metal, rapid loss of amine stabilizer and the development of acidic materials, and apparently the series of reactions producing the decomposition requires the presence of the amine.

The corrosive action of the amines appears to be related to certain specific metals, especially iron (also in its common alloyed form as steel) and copper (alone or in its alloyed form as brass). On the other hand, aluminum, which is known to be an agent for metal induced decomposition insome cases, does not initiate the corrosion reaction inamine-stabilized systems.

In referring to amines in the foregoing paragraph, we have used the term in'its' broad sense. The other organic bases specified in the Dinley patents, including cyclic compounds characterized by nitrogen in the ring, such as pyridine and morpholine, for example, are included within the meaning of this term. Among the suitable amines which are listed in the examples set forth hereinafter, and which are accordingly suitable in the practice of this invention are pyridine, disec butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, n-methyl morpholine, triethylamine, and hexylamine.

The exact mechanism by which the amine reacts with the chlorinated hydrocarbon in the presence of the metal is not completely known or understood. It may be that the amine, being a strong base, that is, a Lewis base and an electron donor, either forms a covalent bond with one carbon atom of the unsaturated chlorinated hydrocarbon, and the resulting fragment reacts with the metal, or, in the case of chlorinated hydrocarbons containing hydrogen, the amine may react by first removing a hydrogen to yield ionic fragments which in turn are reactive toward metals-the end products of such reactions being more or less complex metal-organic chloro compounds. Then again, the metal may be the initiator of the set 'of reactions which involve the amine and the chlorinated solvent.

One explanation for the reaction is that the unsaturated chlorinated compound, being amphoteric, that is, having one carbon basic and the other acid at the unsaturated bond, and the amine being basic, that is, a Lewis base and an electron donor, forms a covalent bond at the acidic carbon leaving the resultant fragment basic and that a metal brings about chelation. It may be that the basic fragment, or the electron donor amine itself holds the metal in the active state as opposed to the passive state (according to the Electron Theory of Corrosion in Corrosion Handbook by Uhlig) so that the active metal reacts with the solvent or the amine stabilizer, forming organo-metallics which are agents which hasten. normal oxidation or at least remove the stabilizer as such and thus reduce the concentration of stabilizer to sub minimal levels, and at the same time cause seriousattack on or corrosion of the metal. In any event, serious corrosion problems are encountered when a lowboiling unsaturated chlorinated hydrocarbon is stabilized with an amine and the product exposed to a ferrous metal, or copper, particularly when the hydrocarbon is for the lower. boiling unsaturated chlorinated hydrocarbons. Other objects and advantages of this invention will further appear hereinafter.

In accordance with this invention, the corrosive action of the organic amine in the presence of metals in the chlorinated hydrocarbon is overcome by incorporating into the mixture a small amount of a substituted aliphatic epoxy compound which interferes with the corrosivev action of the amine in the presence of ferrous metals. The substituted aliphatic epoxy compound does not interfere with the stabilizing action of the amine or its ability to act as an alkaline material or to act as a reducing. agent. It. appears that these substituted aliphatic epoxy compounds act to retard or interfere with the corrosive activity of the amine by either hindering the amine itself, or by forming a protective layer over the surface of the metal. In the former case the amount of substituted. aliphatic epoxy compound required to control the action of the amine is related to the amount of,

amine used, while in the latter case the amount of substituted aliphaticepoxy compound required is related to the surface area of the metal exposed to the solvent andamine'.

It has been found that in a few cases, if the amine,

when used in the usual stabilizing concentration, reacts with the chlorinated solvent and the metal exposed to the stabilizer and' solye'nt, the activity can be reduced by using a greatly increased concentration of stabilizer as, for example, about ten times the usual stabilizing amount. It is believed that the very large amount of amine stabilizer is able to form a protective coating over the metal surface, thusinterfering in the reaction between the amine, solvent and metal. That method of controlling the activity of amine is not desirable because such large amounts of amine add to the cost of stabilizing thev solvent; moreover, if under some condition the concentration of amine should become depleted, the concentration' would fall into that level where the reactivity of the amine would-- rapidly increase and the corrosion difficulties mentioned above would be encountered.

The substituted aliphatic epoxy compounds of this invention havethe following general formula:

Where K may be an alkyl radical. such as C H2 +1, where x is an integer from 1 to 3, or an alkene group or a prenyl group, the following substituted aliphatic epoxy compounds are illustrative:

(l) Glycidyl methyl ether (4 Glycidyl 'phenyl ether 5) Glycidyl allyl ether In accordance with this invention; the crude unsaturated chlorinated hydrocarbcn, prior to the refining opproportion of a substituted aliphatic epoxy compound as described above.

The resulting mixture is heated in a still, which volatilizes the amine and chlorinated hydrocarbon. The substituted aliphatic epoxy compound may be only partially volatilized. Since the severe corrosion problem occurs in the substantially anhydrous liquid phase, the substituted aliphatic epoxy compound is retained at the location where it is most needed. At the same time, the amine stabilizes the chlorinated hydrocarbon in the liquid and vapor phases.

Unsaturated chlorinated hydrocarbons such as trichlor- 1 ethylene and perchlorethylene are widely used as degreasing, solvents, cleaners and the like. For example, ferrous metals are degreasedcommercially by subjecting them to liquid and to vapor phase chlorinated hydrocarbons. Sincethe'liquid hydrocarbon is heated and contains amine, and since it is anhydrous and in the liquid phase, there issome danger of corrosion of the degreasing apparatus orof the metal immersed inthe liquid. Accordingly, it is commercially advantageous to provide a chlorinated hydrocarbon solvent which contains both an amine and a substituted aliphatic epoxy compound in accordance with this invention. g

It is well known that the proportions of amine stabilizers may vary from tracevalues (such as .01% by weight or less) to as high as 1.0% by Weight, based on theweight of the chlorinated. hydrocarbon. However, a range-of the order of about .02.20% by weight represents the'proportions considered commercially preferable in most amine-stabilized chlorinatedhydrocarbons. Amine stabilizers have beenwell known and extensively used, and: different amines have been used in different proportions for different chlorinated hydrocarbons. The art is, well aware of. the proper proportions of each specific amine stabilizer in each specific chlorinated hydrocarbon, and such proportions are conventionally'referred to as' stabilizing proportions, and are so defined herein.

The proportions of the substituted. aliphatic epoxy compound may be varied from about .0l'% by weight to about 5% by weight, but a' range of about .01-.15% by weight is preferred. Such proportions are referred to as inhibitive proportions, and are so defined herein. Preferably, the weight of. substituted aliphatic epoxy compound is about 1-5 times the: weight of amine stabilizer. The

eifect of these substituted aliphatic epoxy compounds is.

shown in the results of tests described below:.

A chlorinated hydrocarbon is refluxed in the presence of a weighed piece of metal. A stabilizing amount of an. amine is added and. the solvent refluxed continuously. After refluxing for at least 48 hours the solvent is titrated for alkalinity and the metal weighed to determine the loss of metal. Similar tests, in which an inhibitin amount of substituted aliphatic epoxy compound has been added along with the amine, are run. Also tests, in which the substituted aliphatic epoxy compound is used alone without amine, are run.

Asused throughoutthe present specification and claims, the term substitutedaliphatic epoxy compound isintended to define the typecompounds referred to in the specification hereof, in which all of the substituent groups comprise carbon and hydrogen with oxygen appearing as indicated in the general formula. Epoxy compounds containing halogen are thus specifically excluded from the substituted aliphatic epoxy compounds of the present invention.

The foregoing: reflux test has been used in industry to evaluate chlorinated solvents for use in such processes as degreasing; Since the test is not particularly severe it TABLE IA and hexylamine, and having a boiling point near that of the chlorinated hydrocarbon in a stabilizing proportion in an amount of from about .01% to about 1.0% by Weight of said solvent, said amine-stabilized solvent in the presence of ferrous metals causing metal corrosion, in combination with an inhibitor for said ferrous-metal amine corrosion comprising a glycidyl ether corresponding to the general formula Inhibitory Efiect on Steel Substituted Epoxy Compounds in Trichlorethylene Amine, Subst. Epoxy Compound Added, Hours Loss of Loss of Metal, Amine percent percent by weight of Test Alkalinity, MgmJFt.

by weight p.p.m. HCl

Triethylamine (Commer- 02 None 39. 82.0 3, 800.

cial Grade) Do 02 .05% Glyeidyl Methyl Ether 116. 0 50. 0 No Corrosion. Do 02 .10% Glycidyl Methyl Ether. 116. O 43. 2 Do.

TABLE IB Inhibitory Effect on Steel of Substituted Epoxy Compounds in Perchlorethylene Subst. Epoxy Compound Added, Hours Loss of Loss of Metal, Amine Percent percent of Test Alkalinity, MgnL/Ftfi p.p.m. H01

P y ri din e (Commercial 02 None 120 59. 4 122.

Grade) D do 120 230.0 348.

. 02 .05% Glycidyl methyl ether 72 65.0 No Corrosion. .02 0 88 64.0 D0. 02 .02% Glyeidyl methyl ethe 88 65. 0 Do. 02 .01% Glycidyl methyl ether. 88 75. 0 Do. L 02 .005% Glyeidyl methyl ether 88 75. 0 Corrosion. 02 .002% Glycidyl methyl ether.-. 88 75. 0 D0. .02 None 72 72.0 585. e .10 do 72 96.3 668. 02 .05% Glycidy-l methyl ether. 87 56. 7 No Corrosion. 02 .05% Glycidyl isopropyl ether- 87 61.0 D0. 02 .05% Glycidyl allyl ether.. 87 59. 0 D0. .02 None 16 71. 0 Heavy Corrosion. 02 .05% Glycidyl methyl ether 96 46.0 No Corrosion. .02 do 88 46. 0 D0. 02 .02% Glycidyl methyl ether.--" 88 72. 0 Do. 02 .Ol% Glycidyl methyl ether 88 74. 2 Do. 02 .005% Glycidyl methyl ether 88 75.4 Corrosion. 02 .002% Glycidyl methyl ether 88 75.4 Do. 02 .05% Glyeidyl methyl ether- 144 51.0 N o Corrosion. 02 144 41. 6 Do. .02 87 41. 0 D0. .02 87 55. 5 D0. 02 87 38. 7 Do.

The beneficial effects observed in Tables IA and IE H H H were not the result of a stabilizing property of the subst1- H I 1 I O R tuted epoxy compound itself. Several anti-oxidants or 7 stabilizers which are known in the art and accepted as 0 H effective inhibitors were added to the chlorinated solvent along with an amine. No inhibitory effects on the action of the amine were observed. If anything, the activity of the amine was increased, as indicated by the fact that attack on the metal was initiated somewhat sooner than when the amine is present alone. Also, in a number of cases, the tests were discontinued while the solvent was still alkaline, and in spite of this fact, considerable attack on the metal had already taken place. This indicates that the corrosive action on the metal is not the result of a lack of stabilizer or the action of an ustable solvent.

Having thus described our invention, we claim:

1. A stabilized solvent which is substantially non-corrosive to ferrous metals consisting essentially of a volatile low-boiling low moleculer weight unsaturated chlorinated hydrocarbon selected from the group consisting of trichlorethylene and perchlorethylene, and which is normally subject to decomposition by metals and oxygen containing an organic amine selected from the group consisting of pyridine, di-sec. butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, N-methyl morpholine, triethylamine,

where R is selected from the ground consisting of an alkyl radical having the formula C H where x is an integer from 1 to 3, the allyl radical and the phenyl radical, said corrosion inhibitor 'being present in an amount from about .01%5% by weight.

2. The stabilized solvent defined in claim 1 the glycidyl ether is glycidyl methyl ether.

3. The stabilized solvent defined in claim 1 the glycidyl other is glycidyl ethyl ether.

4. The stabilized solvent defined in claim 1 the glycidyl ether is glycidyl isopropyl ether.

5. The stabilized solvent defined in claim 1 the glycidyl ether is glycidyl phenyl ether.

6. The stabilized solvent defined in claim 1 the glycidyl ether is glycidyl allyl ether.

7. In a process wherein a volatile unsaturated low molecular weight chlorinated hydrocarbon selected from the group consisting of tn'chlorethylene and perchlorethylene, is exposed in the hot anhydrous liquid state to a ferrous metal, said hydrocarbon including a stabilizing proportion of an organic amine selected from the group consisting of pyridine, di-sec. butylamine, diisopropylwherein wherein wherein wherein wherein '2' amine, diethylamine, n-butylamine, amylamine, methyl pyridine, .N-methyl'morpholine, triethylamine and hexylamine, and which normallyreacts with the chlorinated hydrocarbon and ferrous metal in the presence of said metal .to :corrode saidmetal, =lthe .zamount-ofisaid amine being from about .01%-to about 1.0% by weight of said solvent, the improvement which comprises incorporating into the said chlorinated hydrocarbonand amine about .01-% by weight of an inhibitor forsaid ferrous metalamine corrosion comprising a glycidyl ether having the general formula where R is selected from the group consisting of an alkyl radical having the formula C H where x is an integer from 1 to 3, the alkyl radical and thephenyl radical.

8. The process defined in claim 7 wherein the glycidyl ether is glycidyl methyl ether.

9. The process defined in claim 7 wherein the glycidyl ether is glycidyl ethyl ether.

10. The process defined in claim 7 wherein the glycidyl ether is glycidyl isopropyl ether.

11. The process defined in claim 7 wherein the glycidyl ether is glycidyl phenyl ether.

12. The process defined in claim 7 wherein the glycidyl ether is glycidyl allyl ether.

13. A stabilized solvent which is substantially .non-

corrosive to ferrous metals consisting "essentially 'of a volatile low boiling low molecular weight unsaturated chlorinated hydrocarbon selected from the group consisting of trichlorethylene and perchlorethylene, which is normally subject to decomposition by metals and oXygen, containing as a stabilizer about .01%.'20% ofan organic amine selected from the group consisting of pyridine, di-sec. butylamine, diisopropylarnine, diethylamine, n-butylamine, amylamine, rnethyl pyridine, N- methyl morpholine, triethylamine, and hexylamine, and having a boiling point near tbatof the chlorinated hydrocarbon, said amine-stabilized solvent in the presence'of ferrous metals causing metal corrosion, in combination Witha'n inhibitor-for said ferrous metal-amine corrosion comprising a-glycidyl ether having the general formula selected from the group consisting of pyridine, di-sec.

butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, N-methy-l morpholine, triet-hylamine, and hexyla-mine, and which normally reacts with the chlorinated hydrocarbon and ferrous metal in the; presence of said metal to corrode said metal, the improvement which comprises incorporating into the said chlorinated hydrocarbon and 'amine about .0l% 5% by weight of an inhibitor for said ferrous metalamine corrosion comprising a glycidyl etherhaving'the general formula where R is selected from thegroup consisting of analkyl radical having the formula C H ,-where x is aninteger from 1 to 3, the .allyl radical and the phenyl radical.

Refereuces'Cited inthe file of this patent UNITED STATES PATENTS 2,509,620 Watsonet a1. 'May 30,1950 2,797,250

Copelin June 25, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,031,410 April 24 1962 Wilbur H. Petering et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, lines 1 to 3, strike out "In accordance with this invention, the crude unsaturated chlorinated hydrocarbon prior to the refining opamine. The stabilized product is combned wht an n"; column 5 line 64., for "ustable" read unstable Signed and sealed this 9th day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A STABILIZED SOLVENT WHICH IS SUBSTANTIALLY NON-CORROSIVE TO FERROUS METALS CONSISTING ESSENTIALLY OF A VOLATILE LOW-BOILING LOW MOLECULER WEIGHT UNSATURATED CHLORINATED HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF TRICHLORETHYLENE AND PERCHLORETHYLENE, AND WHICH IS NORMALLY SUBJECT TO DECOMPOSITION BY METALS AND OXYGEN CONTAINING AN ORGANIC AMINE SELECTED FROM THE GROUP CONSISTING OF PYRIDINE, DI-SEC, BUTYLAMINE, DIISOPROPYLAMINE, DIETHYLAMINE, N-BUTYLAMINE, AMYLAMINE, METHYL PYRIDINE, N-METHYL MORPHOLINE, TRIETHYLAMINE, AND HEXYLAMINE, AND HAVING A BOILING POINT NEAR THAT OF THE CHLORINATED HYDROCARBON IN A STABILIZING PROPORTION IN AN AMOUNT OF FROM ABOUT .01% TO ABOUT 1.0% BY WEIGHT OF SAID SOLVENT, SAID AMINE-STABILIZED SOLVENT IN THE PRESENCE OF FERROUS METALS CAUSING METAL CORROSION, IN COMBINATION WITH AN INHIBITOR FOR SAID FERROUS-METAL AMINE CORROSION COMPRISING A GLYCIDYL ETHER CORRESPONDING TO THE GENERAL FORMULA 